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Engine Misfires, P0300, P0303, P0304 Keeps swapping codes

9K views 17 replies 3 participants last post by  dami3n 
#1 ·
Hi guys, need some advice here.

A while back my timing belt snapped causing all the valves to bend. So I took the engine apart replaced all the valves, got new gaskets torqued everything up. The pistons seemed fine they held water didn't do a compression test on them though because I don't own one.

Put the whole engine back together. Then I started her up. She struggled at first as she had been up on her side for a month.

Anyways got her going and noticed on idle it was juddering. The abs light came on to start with but this is probably rust that's got into the sensor with it being up for so long and the wheel off.

I revved the car up and the juddering wasn't noticable I kept it at a constant speed (in neutral) and the Engine light came on.

I have a cheap code reader so I plugged it in. It showed code P0300 P0302 and P0302 P (not sure what the P is for)

Did a sort of compression test where you turn the car over and feel the air that comes out of the cylinders of course its not accurate but it did feel to have some force behind it.

So I thought maybe its the leads or plugs. Swapped them round and whiped the codes. Started her up same problem but now I had p0300 p0303 p0303p so I thought bingo coil pack leads plugs get em changed....

So this morning put new coil pack in with leads new plugs and started her up.

Same juddering again. I let her idle for a bit and she decided to cut out after a few minutes. I stared her again and rise it to a costant speed like before and the light came on again. Flashing light not constant. The light comes on when you rev the car for a while not too high mind.

This time im getting P0300, P0304 It just can't seem to make up it's mind whats wrong with it!

It seems quite odd for the error to keep changing cylinders.

Id like to get some advice from your guys before I start doing more work to it. I wouldn't have thought it would be a compression issue if the codes keep jumping cylinders.

Any help would be great.

Renault clio 1.2 16v MKIII
 
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#2 ·
hi, firstly i asumme you grinded the valve whilst fitting, secondly, are you sure you set the tappets correctly. this seems to be temperature related. if vehcle idles with warning light on remove one plug lead at a time, engine will go off that cylinder with a noticable drop in idle, do each cylinder to see if the drop is the same across each cylinder, if not then you will have found if a cylinder is not firing or holding compression well. good luck, dapa.
 
#3 ·
valves have been lapped tbh they werent at all bad. Tappets didn't need adjusting they were within the tolerance. Its an odd one really.

I have a bloke coming over with a compression testing kit and a better code reader than mine. Hopefully Ill be able to at least find out if there is a compression problem and maybe have more information on the error codes.
 
#4 ·
Ok, so got a bloke to come around and do a compression test. Working from the flywheel side Cylinder 1 - 4

Cylinder one is showing signs of really low compression. Cylinder 2 - 3 is a bit better but both the same rate of compression. Cylinder 4 is working as normal.

Going to take off the timing belt again re do and try again. It might be just the belt that's jumped a tooth. If that don't work looks like im taking the valve cover off again to have a nosey and if still no look it looks like taking the head off to check the valves seating...

Worse case scenario is a cracked piston.... fingers crossed it's not. I think ill try testing it with a bit of oil down the spark plug hole and test the compression.

Am I right to think if the pressure increases then there is a problem with the pistons??!?!?!
 
#6 ·
I took the new ones out and noticed one was oiled up I believe it was cylinder no2 really should have double checked.

Re did the timing belt noticed that the tensioner lugs were slightly bent some how... anyways reset restarted.

Still persistent problem no error codes but clearly juddering hard and there is a leak of what smells like petrol dripping from the exhaust could just be condensate though.

Ive been told many things from timing out, fuel injectors clogged, cracked piston head or a vaccum link some where. It may be the actually valves are out from the belt snapping not too sure would hate to have to take the bleeding head off again to check the valves...

Looks like another head scratching day
 
#7 ·
Ok, update on the situation.

Ran the car with a small tub under the exhaust. Revved the engine a little then went to the rear of the vehicle.

No warning lights came on still noticeable juddering.

There was grey to black water accumilating in the tub. I then took the dipstick out of the engine block and felt around. Feels like air is coming out not puffing more like a flow, a weak flow of air but noticeable.

Check the car to notice engine light flashing (great)

I then returned to the rear and I swear for a brief moment I saw small puffs of white smoke.... (Big no no)

So really it is looking like a damage piston... considering 3 cylinders are low on compression 1 being flat as a fart... The cylinders held water when the engine was being repaired so I "assumed" compression would be fine.

So yeah... if anyone can think of anything else that might help this situation id like to know before going in for a pricey engine swap....

Is it possible to do a leak down test where you just pour oil down the spark plugs and test the compression? Or is this something that might damage the car?
 
#9 ·
Im currently in process of taking it apart again. I noticed there was oil in the air pipes that go from the engine to the intake manifold. Is there a way to test the injectors when the manifold is off the car? Ohm testing or something? Ive seen people do it when the cars running but you just cant get to these plugs on this car there so awkwardly positioned.

Removing the rocker cover there was no obvious leaking or anything. I think im going to go through everything with a fine tooth pick here :\
 
#10 ·
Ok, so got the head off again. I tested the fuel injectors the connections are fine showing acceptable levels for a cold plug. There wasn't any obvious leaks anywhere. Im not going to test the injectors when there off as it's a bit iffy, ill have to test them when there back on the motor, but I really don't think that's the problem.

I have attached a picture of the head below:

Left is cylinder 1 - 4 ( 4 - 1 in Renault eyes) bottom of the picture is the exhaust and the top is the inlet. The 4th cylinder show no signs of any marks or anything but then again the compression is off on that one however there was a tiny bit of oil inside the cylinder walls it might have fallen in when taking the head off.

I tested the 4th piston and its holding water no leaks or anything so its bizarre why there would be a compression issue. It's pointing to the seating looks like ill have to do it again and make sure its done properly this time and look into the guides there.

I noticed that cylinder 1 was black I wasn't aware that it went black that fast. The valves stems are caked in black and same with the chamber the valve stems on the exhaust side are all black aswell this was the chamber that was showing full compression.

When taking the exhaust gasket off I noticed a blackening around the 1st cylinder at the back where the exhaust outlet is could my compression be down to a leaky exhaust gasket?!?!?

2 of the valves where quite hard getting out of the head which isn't a promising sign. I don't think these valve guides can be removed on this engine. Also the keepers, bloody hell they were stuck on the stem heads even using a spring compressor was quite hard work this time around.

hmmm im going to clean the head up and look for any other problems that might have caused the compression issue. Still getting a cylinder 3 engine error code which is actually cylinder 2. Didn't notice any obvious leaks there either. Could be a very tiny tiny hole but it was showing some compression. Didn't see signs of a head gasket leak either.

 
#11 ·
Had the head gasket held as can only see head not block ,,no issues with valve stem seals,are you sure timing was correct.why are you using water ,,thats a new one on me ,have always used diesel .you could be rusting the rings in place and giving yourself other issues..get all 4 pistons level fill all four with same amount of diesel leave 15 minutes and check if all still about the same look to the head
 
#12 ·
Timing was spot on it's a strange one. Had to use water as it's all I had to hand waited 15 minutes with that and no leaks. Diesel isn't something I have just lying around and the local petrol station is quit a fair walk away.

The engine block had no signs of oil on it apart from the tiny bit in cylinder 4 on one side of the wall.
 
#14 ·
Ill have to fetch some in the morning and give it another go and yeah gaskets aren't cheap! joke considering what they are made from! Plus it was a real ball ache getting gaskets for this car....

Ill clean up the head valves etc double check everything then re test with some diesel in the morning. Even if the pistons are knackered could always sell the head to put towards another engine ;)
 
#15 ·
NOOOOOOOOOOOOOOOOOO ,Sump off big ends off pistons out the top new rings .Build back up get it hot and red line it for 20 minutes in the drive on the pedal till it red lines then off let it idle for 30 sec and back red lining it Car will be amazing
 
#16 ·
Yes but.... if its 2 pistons that need doing wouldn't it be cheaper and more effective to just swap engines.... especially if its not just the rings that are bad. Plus what if it needs the cylinders re doing new sump gasket new oil refill etc. Cost me near enough £25 in oil to refill her up :\
 
#17 ·
But this way you know you have a good engine .How would you know the engine you get has no problems ...you can hear the other engine running at scrap yard but.you arent able to test it properly ,,you have already done the top half of the engine .you will still need oil and oil filter .which ever way you go .at least with the engine you have you know mains and big ends are ok under load.its a set of piston rings you would need to buy ,,,
 
#18 ·
Well i tested everything fuel injectors, timing, lapped valves again, re did the tappets every one of them some were far too tight/loose especially the inlet side. Probably what was causing the missfires tbh.

Started her up and no more noticeable misfires or error codes as of yet. But waters coming out of the exhaust and a tiny bit of smoke. Probably that ring is wearing out a bit.

I have a compression tester but it doesn't fit the spark plug holders. I had to use a rubber bung and hold it down and give an estimated reading which isn't very accurate.

Need to locate a correct compression tester for this car as I need to get more accurate readings for a leak down test to see how bad the issue is. Any ideas where I might be able to get one from? Majority of the testers are cheap bits of kit with a gauge and a screw on piece that's about it.
 
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